This paper gives a brief description of a LiDAR Crop Scanner (LCS) and associated software for recording and processing sequential range measurements of tree-row structures. The data processing methods have been described in previous publications (Walklate et al., 2002 and Walklate and Cross, 2013). The results of apple orchard measurements show examples of outputs from the software that are aimed at improving grower access to information about Pesticide Adjustment to the Crop Environment (PACE) for making orchard-to-orchard dose adjustments with conventional sprayers and for making tree-to-tree dose adjustments with precision sprayers.

A concerted effort was made over a 2 year period (2012-13) to transfer the webpage linked PACE (Pesticide dose Adjustment to the Crop Environment) (Walklate and Cross 2013a) system into commercial practice in the UK and to test the results of its implementation on 7 commercial tree fruit farms, feeding back the results to growers and industry. The aim of PACE is to support low pesticide-input to pest management called for in the Sustainable use Directive (2009/128/EC) through efficient use of orchard spraying products. PACE seeks to minimise crop-to-crop variation of spray deposits above the minimum for efficacious use (i.e. the deposit achieved by spraying a standard orchard (1, 2, 3 & 4) at the maximum label dose using a farm sprayer operating at the calibrated reference settings). PACE utilises information about: the number of open nozzles used for the reference setting of the farm sprayer, the selected pesticide type, the tree row spacing and at each of three growth-stages requires the grower to assess the target orchards to determine canopy density and the number of working nozzles to treat the target orchard to the full tree height.

In the EU-FP7-BROWSE project (Bystanders, Residents, Operators and WorkerS Exposure models for plant protection products) spray drift data measured in the Netherlands and the UK for orchard spraying are combined to develop a probabilistic empirical model of bystander and resident exposure to spray drift. The model requires data relating to airborne spray to determine dermal and inhaled exposure, and relating to ground deposits, to determine indirect dermal exposure to contaminated ground. The available data can discriminate between full leaf (BBCH 74?92), the intermediate periods (BBCH 61?73 and 93?0) and the dormant (BBCH 0?60) period. For the BROWSE model, reference curves are defined for axial and cross-flow fan sprayers for ground deposit and airborne drift for 0?1 m and 0?2 m heights above ground as functions of distance downwind.

A generalised model of regulated dose adjustment is formulated to examine the potential for reducing the usage of commercial orchard spraying products. The model considers the harmonised regulations for pesticide registration and spray interception by different orchard structures with different distributions of target pest/disease across the tree-row. Different orchard structure standards (i.e. the values of orchard structure parameters that define the limits for safe and efficacious dose adjustment) are used to model the real-world operational constraint of different product types as they are established by the pesticide registration process (i.e. maximum Ground Area (GA) dose rate for safe product use and the manufacturer's Leaf-Wall-Area (LWA) dose rate for efficacious product use). To eliminate the need for a recommended LWA dose rate on the product label a standard ratio of tree height to row spacing is used to express the intersection between the limits for safe and efficacious product use. Light Detection and Range (LiDAR) recordings of commercial pome-fruit orchards are used to determine model inputs. The LiDAR recordings, selected for use in this study, represent a typical sample distribution of commercial orchards of different: tree size, density, cultivation-method, growth-stage, age and variety. The model outputs obtained from LiDAR recordings are grouped to represent the typical uses of different product types, defined by orchard growth-stage and target pest/disease distribution across the tree-row-width. The generalised model of regulated dose adjustment predicts pesticide usage levels in the range 43%–60% of maximum GA dose rate, depending on product type, with very low liability risk to pesticide manufacturers for reduced product efficacy (c. 1 in 200). This compares with predicted usage levels of (72%–88% of maximum GA dose rate) for the equivalent LWA model. The generalised model of regulated dose adjustment will therefore be needed to provide support for new spraying technologies and regulations in order to achieve the full potential for reducing the use of orchard spraying products as pressure for more sustainable fruit production increase in the future.

This paper examines some of the consequences of adopting the Leaf-Wall-Area (LWA) method of dose expression for the registration of plant protection products used in commercial orchards. The examination method uses Light Detection And Range (LiDAR) recordings of a wide range of UK pome-fruit orchards and a generalised dosage model to simulate the results of deposit trials with a broadcast air-assisted sprayer. The results are constrained in accordance with the normal practices of pesticide registration (i.e. the recommended LWA dose rate is assumed to be efficacious and safe to use below the maximum dose per unit ground area). The discussion of results examines new regulatory aspirations for improving the efficiency of pesticide use through the introduction of LWA dose expression and considers the needs for additional information to support spray applications with and without dose adjustment.

This paper establishes a system to support the dose evaluation part of the pesticide registration process so that growers can make more efficient use of different spraying products across a broad range of European orchards and vineyards. The system comprises: a dose adjustment model and a small database of standard target structures (i.e., regional exemplars where efficient and efficacious use of pesticide is obtained at the label dose rate). The model includes a generalised scaling group relationship between the parameters that describe: sprayer output, target row structure and spray volume deposit. The upper limit for dose adjustment is based on the environmental fate of pesticide and this is represented in the model by the ratio of maximum ground area dose rate to minimum efficacious deposit which is normalised for alignment with target structure measurements. The model is used to examine the leaf-wall-area dose rate recently proposed by the European agrochemical manufacturing industry for harmonising pesticide registration. Good agreement is demonstrated between published measurements and model predictions of ground area and leaf-wall-area dose rate variation at constant deposit for a wide range of target structures (i.e., English pome- and stone-fruit orchards and Italian vineyards). The results are used to establish standard target structures for spraying products with different uses. These standards are needed by regulators to: translate between the different methods of expressing dose rate and improve the accuracy of label dose recommendations. The standards are also needed by growers to enable: more accurate calibration of spraying equipment and prediction of the optimum adjustment of label dose rate for different orchards and vineyards.

Our research has shown that when sprays are applied at a fixed recommended dose rate as prescribed on pesticide labels, there is a greater than 6-fold variation in average pesticide deposits between different apple orchards at different growth stages due to variation in tree size and canopy density. In the work, LIDAR (Light Detection and Range) was used to rapidly characterise tree canopies, a breakthrough which enabled such relationships to be investigated and quantified. The work showed that canopy density accounts for 80% of this variation and canopy density and tree height combined account for over 90% of the variation. If the label recommended dose rate gives a certain average deposit which is effective on taller trees with a denser canopy, designated as a standard, then the same average deposit which can be achieved with a lower dose rate on smaller or less dense trees will be equally effective. Thus, there is an opportunity for making significant dose rate reductions in orchards with less dense canopies and/or smaller trees than the standard. In spring 2006, the PACE (Pesticide dose rate Adjustment to the Crop Environment) system of adjusting the dose rate according to tree height and canopy density so that constant average deposits are achieved in a wide range of different orchards throughout the season was launched in the UK. A series of seminars and training courses for growers were held which were attended by over half the industry. In this paper, the five steps that growers were instructed to follow to determine an appropriate dose adjustment are given including the crucial step where pictograms of apple trees of varying canopy density, reconstructed from LIDAR scans, are used to visually assess canopy density. Attendant advice on water volumes, spray quality and spray cover is also presented together with a worked example. Further work is being done currently to extend the scheme to cider apples and other fruit tree crops.

Our research has shown that when sprays are applied at a fixed recommended dose rate as prescribed on pesticide labels, there is a greater than 6-fold variation in average pesticide deposits between different apple orchards at different growth stages due to variation in tree size and canopy density. In the work, LIDAR (Light Detection and Range) was used to rapidly characterise tree canopies, a breakthrough which enabled such relationships to be investigated and quantified. The work showed that canopy density accounts for 80% of this variation and canopy density and tree height combined account for over 90% of the variation. If the label recommended dose rate gives a certain average deposit which is effective on taller trees with a denser canopy, designated as a standard, then the same average deposit which can be achieved with a lower dose rate on smaller or less dense trees will be equally effective. Thus, there is an opportunity for making significant dose rate reductions in orchards with less dense canopies and/or smaller trees than the standard. In spring 2006, the PACE (Pesticide dose rate Adjustment to the Crop Environment) system of adjusting the dose rate according to tree height and canopy density so that constant average deposits are achieved in a wide range of different orchards throughout the season was launched in the UK. A series of seminars and training courses for growers were held which were attended by over half the industry. In this paper, the five steps that growers were instructed to follow to determine an appropriate dose adjustment are given including the crucial step where pictograms of apple trees of varying canopy density, reconstructed from LIDAR scans, are used to visually assess canopy density. Attendant advice on water volumes, spray quality and spray cover is also presented together with a worked example. Further work is being done currently to extend the scheme to cider apples and other fruit tree crops.

This paper presents results from ongoing research aimed at improving broadcast spraying of fruit trees by enabling pesticide users to make adjustments to the label recommended dose-rate that minimise the variability of deposit on different orchard structures. An important building block of this research is a reliable model for predicting the orchard-to-orchard variation of spray volume deposit across a wide range of different orchards. Tree-averaged measurements of leaf deposit are compared with three different scaling-group models that reflect different spray application adjustment strategies: (i) constant dose-rate, (ii) adjustment of the dose-rate for orchard-to-orchard variation of the target-row area, (iii) combined dose-rate adjustments for variations of target-row area and scale of spray application. The additional input parameters required for models (ii) and (iii) are derived from recordings of orchard structure using a tractor mounted LIDAR system.

Concern for human safety and environmental contamination due to the inefficient use of plant protection products for orchard spraying has resulted in a range of practical models aimed at minimising the orchard-to-orchard variation of deposit through suitable adjustment of the label-recommended dose rate (LRDR) to different crop structure parameters. This study establishes a methodology for optimising model selection by using an appropriate database of crop structure measurements. LIDAR recordings of different orchards at different farms and growth stages have been used to construct an exemplar database of UK pome fruit structures. These recordings were processed initially to reduce each database entry to a set of four parameters describing the tree-row structure, namely: spacing, height, width and area-density. An exact model of LRDR adjustment, assuming minimum spray volume loss and based on all four tree-row structure parameters, was used as a comparator to evaluate the relative performance of different approximation models (i.e. typical regression models based on a reduced set of tree-row parameters). Various approximation models that included the scaling effects of tree-row area-density gave significant agreement with the population of LRDR adjustments predicted by the exact model. The following models gave the best agreement in their class for the percentage of adjustments correctly predicted to within an error tolerance ±1/8th LRDR (i.e. 80% for the tree-row area-density model and 93% for the combined adjustment model based on tree-row height and area-density). Other approximation models of practical interest gave less significant agreement with the exact model (i.e. 66% for the tree-row-volume model, 55% for the fruit-wall-area model, 50% for the constant adjustment model, 5% for no adjustment). Unfortunately, the practice of LRDR adjustment is currently undermined by many plant protection products that do not give the appropriate reference conditions necessary to define the worst-case crop structure for which acceptable biological performance may be achieved at the full LRDR. Only products aimed at uses in conjunction with integrated pest management schemes give this type of information and typically for use with specific models of LRDR adjustment that ignore the important scaling effects of area-density.

The ability to estimate the target area of row crops is an important requirement for the development, registration and efficient use of modern crop protection products for tree fruit spraying. In this study we simulated the LIDAR system using a trajectory model of light transmission compare estimates of the spray target area from LIDAR recordings. The branching structure and dimensional detail of typical tree-row targets is generated numerically using an open L-system model. The results show good correlation between the area estimates given by the simulation system and the records.